1. Field of the Invention
This invention concerns a luminaire that has a plate-shaped optical waveguide, and first illuminants arranged on one or more narrow sides of the optical waveguide and designed to couple light into the plate-shaped optical waveguide, the light coupled into the optical waveguide being emitted via a flat side of the optical waveguide in a first radiating direction of the luminaire.
2. Related Technology
Such a luminaire is known from DE 197 55 658 A1 by the applicant, and is sold under the designation AERO waveguide luminaire. This luminaire is generally very popular, since it is characterized by an extremely flat shape and fulfils the requirements of modern office situations. The luminaire can be arranged freely in the room, and makes reflection-free working possible on vertical or strongly inclined screens, since the radiated light is emitted homogeneously over the whole flat side of the plate-shaped optical waveguide element. Since it is impossible to look at the illuminants directly from below, the luminaire also satisfies the highest aesthetic demands.
The luminaire disclosed in DE 197 55 658 A1 can be in such a form that the light of the illuminants is partly radiated upward as indirect lighting. It is also generally known that light which is radiated via an optical waveguide element has less intensity compared with directly radiated light. Accordingly, in the case of the luminaire described here, the indirect portion of the light, which is radiated upwardly, has a higher intensity than the portion of the light which is radiated downwardly via the optical waveguide element. This is usually seen as a disadvantage of the luminaire, since the coefficient of lighting utilization is very small, because of the inefficient direct component.
A further luminaire known from the prior art is disclosed in DE 10 2005 005 454 A1. This luminaire has discharge lamps as first illuminants, the light of the discharge lamps being coupled into a light pipe and radiated by it in different directions. Also, in a preferred embodiment, the luminaire has light-emitting diodes (LEDs), which are used to generate color effects. The light radiated upwardly from the light pipe for indirect lighting is mixed with the light of the LEDs.